Transition metal oxides constitute one of the most interesting material classes due to their wide variety of interesting and unusual properties. Often these properties are closely related to their defect structure. Within the transition metal oxide community SrTiO3 is often referred to as a model material due to its well known defect chemistry. Therefore, in this work the possibilities of defect engineering are considered for this model material and the resulting properties are utilized for a highly interesting application: Resistive switching of SrTiO3 in a metal insulator metal structure, a field of research where defects are key for the basic operation principle. The interest in transition metal oxides has been accompanied by an increased use of pulsed laser deposition, since it is a powerful and versatile method to achieve epitaxial complex metal oxide thin films. Usually pulsed laser deposition is performed in ultra-high vacuum systems with the substrate being heated. Often oxygen is applied for the process as a method to compensate possible oxygen loss. The pressure applied in this manner is referred to as oxygen pressure, not considering the influence of residual gases. This thesis presents evidence that this pressure in reality does not correspond to the oxygen partial pressure. The ionization based measurement devices applied to the vacuum chamber can shift the equilibrium of the residual gases, which, for low pressure, cannot be neglected. The result is a markedly lower oxygen partial pressures than the applied oxygen pressure suggests, resulting in an increased oxygen vacancy formation. Within this thesis further a method to inhibit the formation of oxygen vacancies in the considered temperature and pressure regimes is presented. It is found that the formation of oxygen vacancies in SrTiO3 is dependent on its termination. As the termination of SrTiO3 can easily be controlled, this constitutes a practical possibility to engineer the oxygen vacancy formation. Pulsed laser deposition itself is a non-equilibrium growth technique, thus deviations from the equilibrium defect concentration and types are expected. An influence on this non-equilibrium process that was up to now not considered is the radiation resulting from the plasma plume. In this work it is shown that the plasma plume present during \STO\: depositions emits UV-radiation, which in turn enhances the oxygen vacancy formation. Besides this, a the possibility to control the cation stoichiometry of the film by a change of the laser fluence is investigated. This method is employed to modify the Sr/Ti-ratio and a Sr-surplus is identified to be highly advantageous for the switching performance of SrTiO3 devices. Two main accommodation mechanisms for Sr-excess are identified, namely Ruddlesden-Popper-type anti phase boundaries and SrO surface segregation. This work presents methods to engineer both defect scenarios in nominally stoichiometric thin films. Ruddlesden-Popper-type anti phase boundaries can be achieved by the stabilization of additional SrO on the substrate surface, which acts as a seed for their formation. SrO surface segregation can be achieved by depositing additional SrO on top of the thin film. These defect engineered thin films are subsequently investigated with respect to their switching properties. It is found that Ruddlesden-Popper-type anti phase boundaries in SrTiO3 result in forming free switching, a highly desirable property for resistive switching devices. Additional SrO on top of the film is shown to form SrCO3, which in turn is a main influence factor on all resistive switching properties. Its heat confinement is shown to determine the memory window and the variability; its high diffusion barrier for oxygen is shown to determine the memory's time stability and the forming step. Summarizing, this works elucidates the sources of defect formation for the model material SrTiO3, shows methods to control the formation of these defects and explains their role for the properties of the material. The presented results in principle apply to other resistive switching oxides in the same fashion and provide a guideline on how to improve the device performance by defect engineering
